An air intake device has been known in which gas flow is formed in a combustion chamber of an internal combustion engine by controlling the opening area of an air intake passage of an intake manifold. This type of the air intake device has been used in cold districts, and measures to discharge moisture content from around a control valve has been taken so as to suppress that moisture content in intake air flowing to the air intake device adheres to a rotation shaft of the control valve and it is frozen.
For example, in a patent document 1, a water collection groove is provided on the bottom wall of a housing to suppress the intrusion of moisture content into the gap between the rotation shaft of a control valve and a bearing. Both of the end parts of this water collection groove are inclined such that the center part of the housing bottom wall becomes low, and the water collection groove extends over the entire length of the housing in an intake air flow direction.
However, in the above water discharge structure, even when the valve is closed, a gap appears between the control valve and the housing bottom wall caused by the water collection groove, and gas flow (for example, tumble flow and swirl flow) becomes low due to air leak from this gap.